Name four sensors used in I.C. engine and explain working of any one.
Sensor used in IC engines ( Explanation of any one )
A sensor is an input device that provides variable information on an engine function. Examples of sensors include the airflow sensor (AFS), crank angle sensor (CAS), throttle potentiometer sensor (TPS) etc, and these provide data on load, rpm, temperature, throttle opening etc. This data is signaled to the ECM, which then analyses the results and computes an output signal. The output signal is used to actuate an n output device.
Crank angle sensor: A permanent magnet inductive signal generator is mounted in close proximity to the flywheel, where it radiates a magnetic field. As the flywheel spins and the pins are rotated in the magnetic field, an alternating (AC) waveform is delivered to the ECM to indicate speed of rotation. If a pin is intentionally omitted at two points on the flywheel, or by contrast a double pin is used, the signal will vary at these points, and a reference to TDC will be returned to the ECM. The location of the positional signal is not at TDC, but may be some other point fixed by the VM. When used, the CAS provides the primary signal to initiate both ignition and fuelling.
Air Flow Sensor (AFS): The AFS is normally located between the air filter and the throttle body. As air flows through the sensor, it deflects a vane (flap) which wipes a potentiometer resistance track and so varies the resistance of the track and generates a variable voltage signal.
Manifold absolute pressure (MAP) sensor: The MAP sensor measures the manifold vacuum or pressure, and uses a transducer to convert the signal to an electrical signal which is returned to the ECM. The unit may be designed as an independent sensor that is located in the engine compartment or integral with the ECM.
Coolant temperature sensor (CTS): The CTS is a two-wire thermistor that measures the coolant temperature. The CTS is immersed in the engine coolant, and contains a variable resistor that usually operates on the NTC principle.
Throttle Position Sensor (TPS): TPS is provided to inform the ECM of idle position, deceleration, rate of acceleration and wide-open throttle (WOT) conditions. The TPS is a potentiometer which varies the resistance and voltage of the signal returned to the ECM. 01 03 MAHARASHTRA STATE BOARD OF TECH From the voltage returned, the ECM is able to calculate idle position, full-load and also how quickly the throttle is opened.
Oxygen sensor (OS): An oxygen sensor is a ceramic device 'placed in the exhaust manifold on the engine side of the catalytic converter. The oxygen sensor returns a signal to the ECM, which can almost instantaneously (within 50 ms) adjust the injection duration.